Method and apparatus for monitoring disc pressure during heat treatment of an intervertebral disc

ABSTRACT

A probe system and method for treating an intervertebral disc of a patient are disclose. A probe has a cannula having an open end defined at a distal end and adapted to couple to a power source. A stylet fits into the cannula so that a distal end of the stylet occludes the open end at the distal end of the cannula. The probe system also includes a pressure monitoring apparatus coupled to the stylet, with the stylet including a pressure sensor in proximity to the distal end of the stylet. The pressure sensor communicates with the pressure monitoring apparatus to measure the pressure of the intervertebral disc. The power source delivers power to the distal end of the cannula, causing heating of the disc when the distal end of the cannula is disposed within the disc, thereby relieving patient pain associated with the disc.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119 ofU.S. Provisional Patent Application Ser. No. 60/666,829 filed on Mar.31, 2005 by Podhajsky et al, entitled “METHOD AND APPARATUS FORMONITORING DISC PRESSURE DURING HEAT TREATMENT OF AN INTERVERTEBRALDISC”.

BACKGROUND

1. Technical Field

The present disclosure relates to a method and apparatus for treating anintervertebral disc for relief of back pain. More particularly, thepresent disclosure relates to a method and an apparatus for measuringpressure of an intervertebral disc during heating.

2. Description of Related Art

The curing of back pain is one of the most important objectives ofneurosurgeons, orthopedists, anesthesiologists and neurologists. Backpain is one of the most common forms of pain and accounts for hugeamounts of disability and loss of labor throughout the world. The curingof back pain heretofore has been in the domain of surgery, percutaneousinjection of chemicals into the intervertebral disc, percutaneousremoval by mechanical means of intervertebral discs, RF heating ofperipheral nerves outside of the intervertebral disc to interrupt nervefibers outside of the disc, and various forms of drug and rehabilitationtherapy.

The use of radiofrequency (RF) electrodes and power sources forgenerators is common in the field of neurosurgery, anesthesiology, andcardiology for the destruction of neural tissue. This is typified by theRF electrodes and RF lesion generator systems of Integra Radionics, Inc.in Burlington, Mass., USA. Heretofore, the lesion electrodes are placedat the target site under various types of guidance, includingstimulation, x-ray control, tomographic image control, and stereotacticapparatus. The electrode typically consists of an insulated shaft withan exposed tip which is elevated to radiofrequency potential. A secondelectrode, usually a dispersive electrode with a large area, is placedelsewhere on the body to return the radiofrequency current to the RFgenerator, thereby making the patient's body part of the radiofrequencycircuit. The intensity of radiofrequency current at the exposed tip ofthe radiofrequency lesion electrode causes the heating of the tissue inthe neighborhood of the electrode, and thus the destruction of thattissue. Typically, the tissue has always been either direct neurologicaltissue, such as in the brain or the spinal cord, or muscle tissue, as inthe heart in the case of cardiac ablation.

A typical example of radiofrequency lesion making is for the relief ofvarious types of back pain, as in the case of facet denervation or indirect destruction of low back nerve structures such as the sympatheticnerves or communicating rami. In the case of facet denervation, theelectrode is placed near a small nerve branch which innervates thespinal facet joints and a heat lesion is made which interrupts thenoxious signals emanating from these joints. RF heating is also used fordestruction of ganglia such as the sphenopalatine ganglion or of othernerves which are ramifications of the nerves which exit from the spinalcolumn. The mechanism is a direct interruption of nerves and thus of thepain signals from the affected areas to the spinal cord. Theseprocedures have been effective; however, there are many pain syndromeswhich relate to the region around the intervertebral disc itself. It isvery difficult to achieve a comprehensive destruction of the nerveswhich innervate the disc. This is because the disc is innervated bymultiple nerve branches. Some of these branches lie close to the exitingspinal nerves, notably those which innervate the clinically importantposterior part of the disc. Destruction of these branches with a heatlesion would therefore carry the risk of damaging the spinal nerves. Itwould be a very effective treatment for so-called discogenic back painto be able to simply and with a minimal number of percutaneous needlesticks denervate or destroy the numerous nerve structures which arepresent at the surface of the entire disc without endangering theimportant nerve structures inside and exiting from the spinal canal.

It has been a characteristic of RF lesion making in the nervous tissueor in the soft muscle tissue that the RF electrode, which affects theheating, be placed in proximity to the tissue to be destroyed. That is,by various stereotactic means such as X-ray, fluoroscopy, computerizedtomography (CT) guidance, magnetic resonance (MR) guidance, orstimulation and recording, the tip of the RF electrode is placeddirectly on or very near the target nerves themselves and the heating issubsequently carried out.

As alluded to above, one of the outstanding problems in the treatment ofback pain relates to neural structures that innervate the intervertebraldisc itself. There are numerous sensory nerves which cluster at theexterior surface of the intervertebral disc and sense mechanicaldeformations of the disc. These nerves appear to protect againstexcessive stress of the disc wall, which in turn may cause seriousdamage to the disc, such as rupture, bulging, or herniation. In thesituation of an overstressed disc, a rupture can cause extrusion orbulging of the inner material of the disc beyond the external wall withconsequent pressure on nerves in the vicinity. This is one of the mostcommon forms of back pain and usually must be cured by surgery orpercutaneous disc removal. However, another very common form of backpain related to the disc is the mere irritation or stimulation of thenumerous small nerves that innervate the periphery of the disc and senseits mechanical stress. These nerves are found ubiquitously over thesurface of the disc. In the situation where herniation or extrusion ofthe disc has not taken place, yet these numerous tiny nerves arestimulated to produce a painful response, there is no simple surgicaltreatment and the patient may be in extreme pain and distress as aresult. It may be fruitless to attempt to place an RF electrode directlyon these small nerves, as they are distributed over an extensive surfaceof the disc, making it impractical and dangerous to introduce asufficient number of electrodes in to denervate all of them. Moreparticularly, it is not possible to know beforehand exactly which ofthese sensing nerves is causing the problem. Indeed, there may be alarge number of them over the entire surface of the disc in thesituation that the disc is extremely distorted, or alternatively, only asubset of them at one particular location for a more focal disc bulge.

U.S. Pat. No. 5,433,739 issued to Sluitjer et al on Jul. 18, 1995describes a technique of introducing an RF electrode or other heatingelectrode into the intervertebral disc, typically under fluoroscopiccontrol, and heating the entire disc to a temperature significantlyabove body temperature. The heated disc heats the nerves which innervateits surface, and the nerves are destroyed or altered when the heat ofthe disc is elevated to an appropriately high temperature. The nervesare heated and desensitized around the disc by minimal invasion to thebody, while at the same time sparing the larger nerve bundles running inthe vicinity of the disc. This technique produces significant painrelief in a substantial fraction of patients suffering from back pain.Additionally, an indirect radiofrequency lesion method is describedwhereby the destruction of desired neural structures is done not bydirect placement of an RF electrode near the structures, but rather bythe radiofrequency heating of an intermediate structure, which in turndiffuses the heat to the neural structures in a more diffuse and globalfashion.

Associated with indirect or global radiofrequency heating techniques, itis important to be able to monitor presssure, not only at the directpoint of RF electrode heating, but also at remote points in space so asto monitor and control the progress of decreased tissue volume. Thus,there remains a need to provide intervertebral pressure monitoringsystems to carry out the direct and/or indirect monitoring of points inspace relative to the primary RF lesion electrode for safer and moreeffective control of the heating process.

SUMMARY

The present disclosure is directed to a probe system for treating anintervertebral disc of a patient, including: a probe, with the probehaving a cannula with a proximal end and a distal end and having an openend defined at the distal end thereof, and with the cannula adapted tocouple to a power source. The probe also has a stylet having a proximalend and a distal end, with the stylet fitting into the cannula so thatthe distal end of the stylet occludes the open end at the distal end ofthe cannula. The probe system also includes a pressure monitoringapparatus adapted to be coupled to the stylet, with the stylet includinga pressure sensor in proximity to the distal end of the stylet, with thepressure sensor adapted to communicate with the pressure monitoringapparatus so as to measure the pressure of the intervertebral disc. Thepower source delivers power to the distal end of the cannula, causingheating of the disc when the distal end of the cannula is disposedwithin the disc, thereby relieving patient pain associated with thedisc.

The pressure sensor may be disposed in an aperture defined in proximityto the distal end of the stylet, and the pressure sensor may be at leastpartially exposed through the aperture in the stylet, to sense pressurein the disc thereby. The stylet may have a tip at the distal end of thestylet. The tip of the stylet may have an aperture defined therein, andthe pressure sensor may be at least partially exposed through theaperture at the tip, to sense pressure in the disc thereby. The cannulamay be substantially insulated on a surface of the cannula incommunication with the body of the patient including the intervertebraldisc. The cannula may have an uninsulated electrically conductive tip atthe distal end of the cannula. The uninsulated electrically conductivetip may be adapted to couple to the power source such that when thedistal end of the cannula is within the disc, power can be transmittedto heat the disc.

The probe system may further include an impedance monitoring apparatusadapted to be coupled to the stylet by an electrical interface tomonitor the tissue impedance of the patient to confirm the properplacement of the distal end of the cannula inside of the disc. The probesystem may further include a temperature monitoring apparatus adapted tobe coupled to the stylet. The stylet may include a temperature sensor inproximity to the tip of the stylet. The temperature sensor may becapable of communicating with the temperature monitoring apparatus by anelectrical connector interface to measure the temperature of thetemperature sensor near the disc. The temperature sensor may be adaptedto communicate with the temperature monitoring apparatus so as tomeasure the temperature of the intervertebral disc when the tip of thestylet is disposed in proximity to the disc.

The present disclosure relates also to a method of treating back or neckpain of a patient by heating an intervertebral disc. The method includesproviding a probe having a proximal end and a distal end, with thedistal end having a tip. The probe may be operatively coupled to a powersource. The method also includes providing a pressure sensor inproximity to the tip of the probe and a pressure monitoring apparatusoperatively coupled to the pressure sensor via the probe. The methodalso includes delivering power from the power source to the distal endof the probe, causing heating of the disc when the distal end of theprobe is disposed within the disc, to relieve patient pain associatedwith the disc thereby, and measuring pressure of the disc. The step ofdelivering power from the power source to the disc via the probe may beperformed for a period of approximately one minute. Immediatelyfollowing the step of delivering power from the power source to the discvia the probe, the method may further include the step of turning offthe power. Following the step of turning off the power, the method mayfurther include the steps of waiting for a period of approximately oneminute and measuring the pressure sensed by the probe pressure sensor.If it is determined that further treatment is necessary based upon themeasured pressure in that a substantial change in disc pressure to apressure level below a threshold pressure has not been achieved, themethod may further include the step of re-delivering power from thepower source to the disc via the probe causing heating of the disc. Theprobe may be a radiofrequency electrode and the power source may be aradiofrequency generator, and the method may further include the stepsof increasing voltage output of the radiofrequency generator so as tosend current through the radiofrequency electrode into the disc and thusheat the disc by ohmic heating, and decreasing the voltage output of theradiofrequency generator after a change in disc pressure has beenmeasured.

The pressure sensor may be disposed in proximity to the tip of thedistal end of the probe. The probe may have an aperture disposed suchthat the pressure sensor is at least partially exposed through theaperture in the probe, thereby to sense pressure in the disc. Thepressure sensor may be disposed at the tip of the distal end of theprobe. The probe may have an aperture disposed such that the pressuresensor is at least partially exposed through the aperture, thereby tosense pressure in the disc.

The present disclosure relates also to a method of treating back or neckpain of a patient by heating the interior of an intervertebral disc. Themethod includes providing a probe. The probe may have a proximal end anda distal end having a tip. The probe may be operatively coupled to apower source. The method includes also the steps of providing a pressuresensor at the distal end at or in proximity to the tip of the probe anda pressure monitoring apparatus operatively coupled to the pressuresensor via the probe; inserting the probe into the patient so that thetip at the distal end of the probe is positioned inside theintervertebral disc. The method also includes the steps of deliveringpower via the probe to the probe tip so as to heat tissue around theprobe tip when the probe tip is in the intervertebral disc so that theprobe tip causes heating of the interior of the intervertebral disc to atemperature substantially above body temperature by absorption of atleast a portion of the power delivered via the probe tip to the tissueof the intervertebral disc, thereby causing heating and resultantchanges in the disc material and nearby neurological structures torelieve the patient's pain, and monitoring pressure of theintervertebral disc by reading output of the pressure monitoringapparatus operatively coupled to the pressure sensor, and therebyquantitatively monitoring the heating process of the intervertebraldisc. The step of delivering power may be performed for a period ofapproximately one minute. Immediately following the step of deliveringpower, the method may further include the step of turning off the power.Following the step of turning off the power, the method may furtherinclude the steps of waiting for a period of approximately one minuteand reading the output of the pressure monitoring apparatus operativelycoupled to the pressure sensor. If it is determined that furthertreatment is necessary based upon the measured pressure in that asubstantial change in disc pressure to a pressure level below athreshold pressure has not been achieved, the method may further includethe step of re-delivering power from the power source to the disc viathe probe causing heating of the disc.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 illustrates RF heating of an intervertebral disc according to thepresent disclosure, using a single percutaneous electrode;

FIG. 1A illustrates a side elevation view of a portion of the singlepercutaneous electrode of FIG. 1 including a pressure sensor accordingto the present disclosure;

FIG. 1B illustrates a front elevation view of the portion of the singlepercutaneous electrode of FIG. 1A;

FIG. 2 illustrates an embodiment of the present disclosure involving aheating electrode in the intervertebral disc and secondary pressuresensing probes to monitor positions remote from the primary RF electrodelesion site;

FIG. 3 illustrates an embodiment of the present disclosure of anelectrode apparatus for intervertebral disc heating, including specialhubs and cable connections and pressure sensing and temperature sensingmeans;

FIG. 3A illustrates an end view of the electrode apparatus forintervertebral disc heating of FIG. 3 which includes both pressuresensing and temperature sensing means;

FIG. 4 illustrates an embodiment of the present disclosure of a set ofapparatus for intervertebral disc heating, including a radiofrequencycannula with insulated shaft, exposed tip, and plastic hub, togetherwith a universal stylet which has external connection means andimpedance monitoring means, and pressure sensing means;

FIG. 5 illustrates an embodiment of the present disclosure of a set ofcannula plus straight and curved electrodes and pressure sensing meansto make axial or off-axis heating patterns in disc lesioning;

FIG. 5A illustrates a variation of an embodiment of the presentdisclosure of FIG. 5 of a set of cannula plus straight and curvedelectrodes and pressure sensing means and a position control device tomonitor positions of the heating electrode tip with the electrode tip ina retracted position;

FIG. 5B illustrates the variation of the embodiment of the presentdisclosure of FIG. 5A with the electrode tip in an extended position;

FIG. 6 illustrates an embodiment of the present disclosure of aself-contained needle with pointed tip for tissue penetration andpressure sensing means, radiolucent hub, and external connection cables;

FIG. 7A illustrates a side elevation view of a portion of a singlepercutaneous electrode including a pressure sensor and a temperaturesensor according to a variation of the present disclosure; and

FIG. 7B illustrates a front elevation view of the portion of the singlepercutaneous electrode of FIG. 7A.

DETAILED DESCRIPTION

The present disclosure will be understood more fully from the detaileddescription given below and from the accompanying drawings of particularembodiments of the present disclosure which, however, should not betaken to limit the present disclosure to a specific embodiment but arefor explanatory purposes.

Numerous specific details may be set forth herein to provide a thoroughunderstanding of a number of possible embodiments of the presentdisclosure. It will be understood by those skilled in the art, however,that the embodiments may be practiced without these specific details. Inother instances, well-known methods, procedures, components and circuitshave not been described in detail so as not to obscure the embodiments.It can be appreciated that the specific structural and functionaldetails disclosed herein may be representative and do not necessarilylimit the scope of the embodiments.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. For example, some embodimentsmay be described using the term “connected” to indicate that two or moreelements are in direct physical or electrical contact with each other.In another example, some embodiments may be described using the term“coupled” to indicate that two or more elements are in direct physicalor electrical contact. The term “coupled,” however, may also mean thattwo or more elements are not in direct contact with each other, but yetstill co-operate or interact with each other. The embodiments disclosedherein are not necessarily limited in this context.

It is worthy to note that any reference in the specification to “oneembodiment” or “an embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment. The appearances of the phrase“in one embodiment” in various places in the specification are notnecessarily all referring to the same embodiment.

Embodiments of the present disclosure will be described hereinbelow withreference to the accompanying drawings. In the following description,well-known functions or constructions are not described in detail toavoid obscuring the disclosure in unnecessary detail. In the drawingsand in the descriptions which follow, the term “proximal”, as istraditional, will refer to the end of the electrode or probe which iscloser to the user, while the term “distal” will refer to the end whichis further from the user.

RF electrode heating, as described in commonly owned U.S. Pat. No.5,433,739, and which is hereby incorporated herein by reference in itsentirety, destroys neurological structures. To determine the appropriateapplication of heating to destroy neurological structures and releasethe correct amount of pressure on a herniated disc, in addition to meansfor monitoring temperature, or in lieu thereof, a system for measuringthe pressure of the disc is included in the heating system of thepresent disclosure. The system for measuring the pressure in the discincludes a pressure sensor and any ancillary equipment to the pressuresensor. The use of a pressure sensor provides data on the status of thedisc during thermal treatment and provides an indication of the progressof tissue volume reduction during the RF procedure. Once there has beena substantial change in disc pressure, the heating procedure can beterminated. “Substantial change in disc pressure” as used herein refersto a tissue volume reduction in the nucleus of the intervertebral discwhich relieves the subject of back pain. Thereby, the disc pressure hasbeen reduced to a threshold pressure below which the patient no longersenses back pain.

The pressure sensor can be any type of pressure sensing device suitablefor the application. For example, the pressure sensing device may be astrain gauge sensor, an optical strain sensor, or electromechanicalsensor. The pressure sensor may be an electromechanical sensor arraysuch as a micro-electromechanical system (MEMS). The pressure sensingdevice may be included on the RF electrode or may be a separate needleindependent of the RF electrode but placed in the nucleus of the discduring the intervertebral heating procedure.

In addition to the pressure sensing device, ancillary equipment is alsoprovided. Ancillary equipment includes equipment capable of providingenergy such as a power or light source together with circuitry that iscapable of detecting the output of the pressure sensing device andanalyzing and/or converting the output into usable information. Thepressure sensor measures the intervertebral pressure, converts thepressure measurement into an electrical signal, and transmits thepressure measurement to a display. The output may be displayed to theuser in any useful pressure metric such as pounds per square inch (psi),millimeters of mercury (mm Hg), newtons per square meter (N/m² orPascal) or newtons per square millimeter (N/mm²), kilograms per squarecentimeter (kgf/cm²), and the like. The output may also serve as aninput parameter for a control circuit in the RF generator. For instance,the pressure information would then influence the energy output of theRF generator applied to the electrode. If a certain change in pressureis desired, the pressure output can be used to determine the change inpressure as heat is applied to the intervertebral disc.

In one embodiment of the present disclosure, the ancillary equipment canbe included internally to the RF generator. For instance, the pressuresensing device is a transducer contained within the heating system. Inanother embodiment of the present disclosure, the ancillary equipmentcan be enclosed in an accessory apart from the generator but connectedto the RF electrode. In a further embodiment of the present disclosure,the ancillary equipment can be enclosed in an accessory apart from theRF generator and coupled to a pressure sensing electrode separate fromthe RF electrode.

FIG. 1 shows the method and apparatus of the present disclosure, whichinvolves an indirect heating of neural structures by placement of an RFelectrode into the intervertebral disc and a measurement of the pressurein the intervertebral disc, so as to relieve back pain associated withinnervation of the surface of the disc or nearby structures. This ismerely one embodiment of the present disclosure involving an RFelectrode, but could apply equally well to any other probe type whichprovides heat to the disc. Other systems such as thermal and cryogenicsystems described in commonly owned U.S. Pat. No. 5,571,147, which isincorporated herein by reference in its entirety, are included in thepresent disclosure.

Referring to FIG. 1, the electrode 1 consists of a rigid shaft which isinsulated except for its tip end 2. The tip end has a sharpened point 3,enabling it to penetrate the tissue of the body 4 during percutaneousentry. The exposed metal tip 2 represents the active electrode area. Atthe hub 5 of the electrode, there is a connection cable 6 couplingelectrode 1 to a source 7 of radiofrequency power, e.g., an RF lesiongenerator. This RF lesion generator is typified by the products ofIntegra Radionics, Inc. in Burlington, Mass., USA. There is also a cableconnection 8 to a reference electrode 9 that is typically attached to asurface of the body. This RF lesion connection diagram is referred to asa monopolar type arrangement, meaning that there is a single activeelectrode tip 2. The reference electrode 9 typically has a very muchlarger area than the active tip 2, so that there is no heating at thesurface of the body where reference electrode 9 is attached. Theradiofrequency generator includes devices and readouts for monitoringthe pressure at the electrode tip 2. This is illustrated by the pressuremonitoring meter 10. Also monitored is the impedance in the RF circuitthrough the electrodes as indicated by the meter 11. This impedancemonitoring is typical of modern RF lesion generators. The space in theintervertebral disc is of a very special structure and consists of afibrous material with a substantially low electrical impedance. The RFgenerator may also include a stimulator and control circuitry to varyand monitor the radio frequency power delivered to the electrode 1.

As shown in FIG. 1, the RF electrode tip 2 is placed directly into theanatomical intervertebral disc 12. By their nature, the intervertebraldiscs act as cushions or shock absorbers between the bony vertebralstructures 13. Because they are elastic, their surface 14 is subject tostresses, strains, and even injury if the disc is overstressed by excessweight or improper mechanical movements. Such stresses can give rise tothe distortion of the disc and of its surface shape. Such mechanicaldistortions of the disc are monitored by the nerve structures 15 whichare located over the surface 14 of the disc. These neural sensingstructures are distributed widely over the surface of the disc and arethe first warning signs of an overstressed disc surface. An overstresseddisc surface can give rise to bulging, herniation or even rupture, whichis one of the most common causes of back pain. Thus, these neuralstructures 15 provide natural warning detectors that the disc is beingoverstressed or injured. Frequently, an injured disc will haveirritation to its surface and possibly permanent distortion of itssurface, which will give rise to chronic and continuous pain signalsfrom the neural structures 15. Frequently, the patient will be normal inall other respects, yet the chronic irritation of the nerves 15 givesrise to chronic and debilitating pain. As mentioned above, it isimpractical to consider knocking out each of these neural structures bymultiple placement of numerous RF electrodes near each of them, as inthe case of a direct RF lesion techniques done in the past.

By placing even a single RF electrode in the interior region at position16 approximately at the center of the disc and then heating the regionof the interior disc by applying RF power there, one essentiallyachieves a global spread of heat throughout the disc. This heat thencauses heating of the neural structures 15 which innervate the surfaceof the disc. If properly done with the monitoring of at least one oftemperature and pressure, this process can denervate the neuralstructures 15 on a global or semi-global basis and reduce the tissuevolume in the disc. The degree of reduction of tissue volume in the disccan be measured by measuring the pressure in the disc. Hence, thepatient is relieved of back pain related to stress of the intervertebraldisc and its surface.

Heat produced at the core of the intervertebral disc is spread out overa substantial distance throughout the disc so as to heat its periphery.The reason that the heat can spread so effectively to such a long rangeis that the intervertebral disc material has no vascularity. Becausethere is no blood flowing in the disc, the usual dramatic convection ofheat away from the heated region is reduced essentially to zero. In thisrespect, the disc is strikingly different from all other RF lesiontargets that are heated. Other targets, such as the brain, spinal cord,muscle tissue, etc., are all highly vascular. Thus, the usual diminutionof heating at long range associated with heating the brain tissue andmuscle tissue is absent.

A second factor which enhances the global heating of the entire disc isthat the disc represents essentially a two-dimensional layer between thebony vertebrae above and below it. The bone is a good thermal insulatorand also is not as highly electrically conductive as the disc or normaltissue. Thus, the electrical current from the active tip 2 will tendpreferentially to spread only throughout the disc, and much less throughthe bones above and below it. Heating thereby done within the disc isconfined to the disc as a consequence of the insulative character of thebones above and below it. Thus, the heat spreads quickly and effectivelythrough the entire disc, raising the entire pancake-shaped structure ofthe disc to high temperature. The heat flows to the periphery of thedisc where it heats the neural structures and other surrounding tissue.It is only at the disc periphery that vascularity or convective flowenters the equation of heat balance, and essentially only there the heatis sinked away rapidly in the annulus of tissue immediately outside thesurface of the disc. Thus, one can expect an elevated temperaturethroughout the disc with a rapid fall-off of temperature as one emergesfrom the surface of the disc into the surrounding tissue. However, it isjust in that critical range of the surface of the disc where thetemperature can remain elevated, thereby destroying the innervatingstructures of the disc, and yet not endangering other criticalstructures such as the spinal cord 18 that may be in the vicinity of thedisc. Any substantial heating of the spinal cord 18 could cause severedanger and injury to the patient, including life threatening neuralinterruption. However, by the indirect process of heating thenon-vascular disc with rapid fall-off of temperature by bloodcirculation immediately outside the disc, critical neural structures(e.g. the spinal cord 18) and other neural structures (e.g. the anteriorand posterior nerve roots) are not injured by this process. The factthat the procedure is safe and effective was not at all obvious a prioriin view of the fact that such a large structure is being heated tosignificantly elevated temperatures.

As noted previously, either in addition to monitoring the temperature ofthe electrode tip, or in lieu thereof, the present disclosure includesthe step of monitoring the pressure surrounding the electrode tip. Atypical procedure is to place the electrode 1 percutaneously through thesurface of the patient's skin 4 under X-ray or fluoroscopic interactiveguidance. By taking lateral and anteroposterior views, it is easilyascertained that the proper path of introduction of needle 1 is achievedand that tip 2 resides near the central position 16 of theintervertebral disc. RF current is then applied from the RF generator 7via the cable 6. Cable 6 can be a multiplexing type cable which includesseparate power and instrumentation and control cables to and from the RFgenerator 7. The current enters the disc, spreads out through the discmaterial, and returns out through the body to reference electrode 9 andthen through the cable 8 back to the RF generator 7. Thus, the patient'sbody is part of the RF circuit. The pressure at or in the vicinity ofthe electrode tip 2 is monitored by pressure meter 10. In addition, thetemperature at or in the vicinity of the electrode tip is monitored by atemperature meter (not shown). Typically, and as best shown in FIGS. 1Aand 1B, monitoring of the pressure in the vicinity of the RF electrodeactive tip 2 can be implemented by a pressure sensor 100 built intoelectrode 1 in proximity to RF active tip 2 together with appropriatesensor wires in cable 6 and circuitry in apparatus 7. In particular, theelectrode 1 has a central axis “A” extending from a proximal end of theelectrode 1 at hub 5 to a distal end of the electrode 1 at tip 2. Anaperture 110 is formed and defined in the outer surface of the electrode1 at a distance “d” extending from the distal end of the electrode 1 attip 2. Pressure sensor 100 is disposed within the aperture 110 in arecessed position such that the surface of the pressure sensor 100 atleast partially exposed by the aperture 110 does not protrude beyond theouter surface of the pressure sensor 100. Typically, the distance “d” isabout 0.5 to about 1.0 cm. A pressure sensing cable 120 is coupled tothe pressure sensor or transducer 100 and is routed through themultiplexing cable 6 to couple with the pressure monitor 10. Inaddition, a thermocouple 50 can be disposed at the tip 2 of theelectrode 1. A temperature sensing cable 60 is coupled to thethermocouple 50 and routed also through the multiplexing cable 6 tocouple with the pressure monitor 10.

In particular, pressure sensor instrumentation cable or wire 150 isembedded within the electrode 1 and is coupled to the pressure sensor100 and passes through cable 6 to couple to pressure monitoring meter 10in RF generator 7.

A typical procedure might involve raising the core temperature of thedisc 12 in proximity to the tip 2 at core position 17 to 70° C. or more.There is some fall-off of temperature in the disc out towards theperimeter of the disc at position 21 at the far wall of the disc, butnonetheless the surface of the disc 14 is elevated to substantialtemperatures 50° C. or 60° C. and perhaps higher. These are sufficientlyhigh temperatures to denervate the fine nerve endings 15 which cover thesurface of the disc, thus relieving the patient of pain, but notinducing any pain during the procedure itself.

The electrical resistance, or impedance, of the intervertebral discmaterial itself is substantially lower than surrounding tissue,illustrated in FIG. 1 as the medium 19 that surrounds the entire spinalcolumn 23. Thus, in the progression of introducing the electrode 1through the body surface 4, one observes an impedance which is initiallyrelatively high. Then as one enters the disc space, one sees animmediate reduction of the impedance due to the lower electricalresistance of the intervertebral disc 12 itself. This transition betweenthe normal tissue and intervertebral tissue is direct evidence that thesharpened point 3 and RF active tip 2 of the electrode 1 is in the disc12, and thus in a proper position. Furthermore, when the probe electrode1 is advanced along a path indicated by the dotted line 20 to the point21 where the RF active tip 2 has reached the far wall of the disc atpoint 21, one can again observe an increase of impedance. This increaseindicates that the tip 2 of the electrode 1 is emerging from the otherside of the disc 12. Thus, one has by impedance monitoring a directmeasure of introduction of probe electrode 1 into the disc 12 and thetotal traversal and limits of the probe tip 2 in the disc space interiorregion 16.

More particularly, an example of a method of using pressure monitoringin a feedback loop as a control parameter in conjunction withtemperature monitoring may include the following steps: a) provide theprobe or probe electrode 1 which is operatively coupled to a powersource represented by RF generator 7, the probe having a proximal end,represented by the hub 5, and a distal end, represented by the probe tip2; b) provide the pressure sensor 100 in proximity to the tip 2 of theprobe 1 and a pressure monitoring apparatus, represented by RF generator7, operatively coupled to power source, also represented by RF generator7; c) thermally treat the intervertebral disc 12 in the interior region16 for a duration of approximately one minute; d) turn off power fromthe RF source 7; e) wait for a period of approximately one minute; f)take a pressure measurement; g) determine if further treatment isnecessary based upon the pressure measurement; h) resume thermallytreating the intervertebral disc 12 in proportion to the pressuredifference by re-delivering power from the power source 7 via the probeor probe electrode 1 to the disc 12. If the desired result is notachieved in that the measured pressure indicates that a substantialchange in disc pressure to a pressure level below a threshold pressurebelow which the patient no longer senses back pain has not beenachieved, return to step (c) of thermally treating the intervertebraldisc 12 in the interior region 16 for a duration of approximately oneminute.

The example of the method of using pressure monitoring in a feedbackloop as a control parameter in conjunction with temperature monitoringmay also be implemented to treat back and neck pain of a patient byradiofrequency heating of the intervertebral disc 12 of the patient. Themethod includes the steps of: (a) providing a radiofrequency electrode,e.g., probe or probe electrode 1 having a proximal end, represented byhub 5, and a distal end, represented by the probe tip 2, with theradiofrequency electrode 1 having a substantially insulated shaft 22with an uninsulated conductive radiofrequency tip, represented bysharpened point 3 and exposed metal tip 2, representing the distal end,and radiofrequency connections at the distal end, represented byconnection cable 6, and electrical connections, represented by pressureand/or temperature sensor and/or power cable or wire 150, between theradiofrequency connections 6 and the radiofrequency tip, with theradiofrequency electrode 1 being adapted to penetrate the body of thepatient including the intervertebral disc 12; (b) inserting theradiofrequency electrode 1 into the body of the patient, so that theradiofrequency tip 2 may be placed within the intervertebral disc 12;(c) coupling the external radiofrequency generator 7 to theradiofrequency connection so as to apply a radiofrequency voltagegenerated by the radiofrequency generator 7 to the radiofrequency tip 2via the electrical connection 150; (d) increasing the radiofrequencyvoltage to cause current to flow from the radiofrequency tip 2 into theintervertebral disc 12 when the radiofrequency tip 2 is placed withinthe intervertebral disc 12, thereby causing the intervertebral disc 12to heat up and thus cause changes in the intervertebral disc materialand nearby neurological structures, thereby relieving the patient of thepain; and (e) inserting the pressure sensor 100 be into the disc 12,with the pressure sensor 100 being adapted to monitor pressure in thedisc 12, whereby a diagnostic evaluation of the disc can be made byobserving pressure changes of the disc from heating caused by theradiofrequency tip 2.

The step of increasing the radiofrequency voltage to cause current toflow from the radiofrequency tip 2 into the intervertebral disc when theradiofrequency tip 2 is placed within the intervertebral disc 12 may beperformed for a period of approximately one minute. Immediatelyfollowing the step of increasing said radiofrequency voltage to causecurrent to flow from the radiofrequency tip 2 into the intervertebraldisc 12 when the radiofrequency tip 2 is placed within theintervertebral disc 12, the method may include the step of turning offthe radiofrequency voltage. The method may further include the steps ofwaiting for a period of approximately one minute and measuring thepressure sensed by the pressure sensor probe. If it is determined thatfurther treatment is necessary based upon the measured pressure, themethod may further include the steps of: re-coupling the externalradiofrequency generator 7 to the radiofrequency connection 6 so as toapply a radiofrequency voltage generated by the radiofrequency generator7 to the radiofrequency tip 2, and increasing the radiofrequency voltageto cause current to flow from the radiofrequency tip 2 into theintervertebral disc 12 when the radiofrequency tip 2 is placed withinthe intervertebral disc 12.

The foregoing methods represent an important aspect of the presentdisclosure related to providing at least one pressure monitoring sensorto confirm the correctness of the procedure following introduction ofthe probe electrode 1 into the target volume, i.e., the interior region16 and the far wall of the disc 12 itself.

Another useful target method is using stimulation voltage on theelectrode as the electrode is advanced through the tissue and on intothe disc. Most lesion generators 7 have a built-in stimulator tostimulate neurological structures. By applying the stimulation as oneadvances the probe, first through the intervening tissue 19 and then oninto the intervertebral disc volume 12, any approximation to criticalnerves on that pathway may be detected by continuous stimulation andconsequent physiological or motor response. Once the electrode is withinthe disc volume 12, because there is no innervation of the interior ofthe disc itself, all stimulated responses are absent.

FIG. 2 illustrates embodiments of pressure monitoring at multiplepositions associated with the present disclosure. The probe or probeelectrode 201 again is inserted into the intervertebral disc space 212.The exposed tip 202 of the probe electrode 201 is positioned at or nearthe center of the disc 212. The shaft 280 of the electrode, except forthe tip 202, is usually insulated to prevent heating of tissue otherthan that near the probe tip 202. Again, a cable 206, which may be amultiplexing cable, enables application of RF voltage to the probeelectrode 201, and thus heating of the core of the disc 212.

Since global heating of the disc 212 occurs to destroy neural structuresat long range, monitoring pressure both at the core heating position,namely the point 250 of the electrode tip 202 as well as other points onthe surface 214 of the disc 212 provides a user, such as a painintervention specialist, valuable data on the status of the disc 212.Monitoring of pressure can provide an indication of the progress oftissue volume reduction during the procedure. To illustrate how remotepressure monitoring can be done, an extension 251 emerges from tip 202of the probe electrode 201 and has a pressure sensor 200 a at or inproximity to its tip 252. In a manner as illustrated previously in FIGS.1A and 1B, the extension 251 includes an aperture 210. Typically, theaperture 210 is formed and defined in the outer surface of the extension251 at a distance “d” extending from the distal end of the extension 251at tip 252. The pressure sensor 200 a is disposed within the aperture210 in a recessed position such that the surface of the pressure sensor200 a at least partially exposed by the aperture 210 does not protrudebeyond the outer surface of the shaft 280. Again, typically, thedistance “d” is about 0.5 to about 1.0 cm. An aperture 250 is disposedin the shaft 280 of the probe or probe electrode 201 such that when theextension 251 is in a retracted position wherein the extension tip 252is flush with the shaft tip 202, the surface of the pressure sensor 200a exposed by aperture 210 in the extension 251 is also exposed by theaperture 250 in the electrode shaft 280 so that pressure monitoring bythe pressure sensor is unimpeded.

Pressure sensor instrumentation cable or wire 260 is embedded within theprobe or probe electrode 201 and is coupled to the pressure sensor 200 aand passes through cable 206 to couple to pressure monitoring meters261, 262 and 265 in RF generator 207, which provide readouts forpressure readings P1, P2 and P3, respectively. The tip 252 is shown inproximity to the external surface 214 of the disc 212, and thus thepressure sensor 200 a measures the pressure at that point. By thismeans, the pressure can be monitored not only at the aperture 250 inproximity to which the primary heating is being done, but the pressurealso can be monitored at remote point 252 at the surface of the disc 214which is critical to the denervation of the disc nerves. In addition, atemperature sensor 205 a can be disposed at the tip 252 of the electrodeextension 251. A temperature sensing cable 220 is coupled to thetemperature sensor 205 a and also routed through the multiplexing cable206 to couple with the pressure monitors 261, 262, and 265 within the RFgenerator 207.

Another method of monitoring pressure of the disc 212 is by having aseparate parameter monitoring probe 253 inserted along another route.Typically in a similar manner as described previously with respect toFIGS. 1A and 1B, via pressure sensor 200 b located in proximity to tip256 of the parameter monitoring probe 253, pressure sensorinstrumentation cable or wire 276 is embedded within the probe 253 andis coupled to the pressure sensor 200 b and couples to pressuremonitoring meter 288 in ancillary circuitry 286, providing pressurereadout P4. The pressure sensor 200 b therefore may measure the pressureat the position 254 at another point on the surface of the disc 212. Theprobe 253 can be totally insulated so as to reduce perturbations of theradiofrequency current. Alternatively, it can be a second RF electrodeused in a bipolar arrangement with the primary electrode 201 or as asecondary primary active electrode in the field of the disc 212.Although ancillary circuitry 286 is shown as a separate device, anyremote pressure monitoring sensor may be coupled to a single generator207 to reduce clutter and to enable a single device to monitor theplurality of monitoring points. In addition, as discussed previously, atemperature sensor 205 b can be disposed at the tip 256 of the parametermonitoring probe 253 and used in conjunction with pressure sensor 200 b.

It is also possible to move the extension pressure probe 251 backwardsand forwards over a range. If the tip 252 of probe extension 251 isextended to a distance “D” beyond the tip 202 to position d1, then theentire distance of that range can be monitored. For example, if pressuremeter 261 measures pressure P1 at tip 202 by means of pressure sensor200 a, then pressure meter 262 could measure the pressure P2 at positiond1. Similarly, the probe tip 252 may be withdrawn back up inside of theshaft 280 to a position such as at aperture 255. Aperture position 255is at another point on the perimeter 214 of the disc 212. The pressuresensor 200 a, when drawn back to aperture position 255, could monitorpressure P3 at a second point on the perimeter and be visualized on yetanother pressure meter 265. The independent probe 253 may be monitoredby pressure meter 288 on a separate apparatus or an apparatus combinedin the RF lesion generator 207. The single pressure sensor 200 a can beconfigured to transfer the pressure readings to a multiplicity ofdifferent pressure meters via a multiplicity of different contact pointsinside the probe shaft 280 which are independently wired to themultiplicity of different meters such as pressure meters 261, 262, and265.

Yet another way of measuring the pressure throughout the disc and atremote positions would be to have a side outlet probe 266 with apressure sensor 200 c exposed by an aperture 230 in proximity to the tip267 of the probe 266, with the aperture 230 being disposed in a similarmanner as explained previously with respect to FIGS. 1A and 1B. Pressuresensor instrumentation cable or wire 296 is embedded within the sideoutlet probe 266 and is coupled to the pressure sensor 200 c and passesthrough cable 206 to couple to pressure monitoring meters 261, 262 and265 in RF generator 207, which, as before, provide readouts for pressurereadings P1, P2 and P3, respectively. Such a side probe 266 couldemanate along a curved trajectory (as indicated by the dashed line 272)to access and sample pressure at points transverse to the probe axis.The degree of extension of any of these pressure probes could be gaugedby the scale 268 on the hub 269 of the electrode 201. In addition, alsoas discussed previously with respect to FIGS. 1A and 1B, a temperaturesensor 205 c can be disposed at the tip 267 of the parameter monitoringprobe 266 and used in conjunction with pressure sensor 200 c.

It may also be possible to implement the electrode 201 to have a curvedor flexible tip structure that can access the entire volume of the discand thus deposit the primary heat at different locations within thedisc. This has been illustrated by the TEW electrode of IntegraRadionics, Inc. of Burlington, Mass., USA, and could be applied in thecontext of the present disclosure. Another illustration of such a curvedor side extending electrode for RF heating is discussed below withrespect to FIG. 5.

There are various embodiments of the needle apparatus which areadvantageous to the disc heating procedure. Referring to FIG. 3, thereis illustrated a cannula 301 which has an insulated shaft portion 302(illustrated by the hatched surface) with exposed uninsulated tip 303that has a sharpened, beveled point 304 for penetration of the body intothe disc. The hub 305 of the cannula 301 is made from plastic or lowradiopacity material so that imaging along the direction of the needle314 (which is the combination of the cannula 301 and the hub 305), theso-called “tunnel vision,” or “needle view,” can be implemented withminimal obstructive artifact from the hub. Further, there is a styletsystem which closes off or occludes or obdurates the open lumen (i.e.,the open space 313 inside the cannula 301) of the cannula 301 during theinsertion and possibly lesioning phase. This stylet shaft is indicatedby the dashed line 306, and this shaft 306 extends down to the exposedtip 303 and may or may not have an angled bevel itself so as toappropriately close off the open lumen of tip 303 during the insertionphase. The stylet 306 has a hub 307 which, in this illustrativeembodiment, attaches mechanically to the stylet 306. Further, the stylet306, which may be made from a conductive metal material, has aconnection means 308 which can be coupled by cable connector 309 to acable 310 which can be further coupled to an external apparatus, e.g., agenerator, as described above and in FIGS. 1 and 2. The hub 307 againmay be made from a plastic material in one embodiment of the disclosureso that the tunnel vision view under X-ray or fluoroscopy can be donewith the stylet 306 fully in place in the cannula 301. One has theadvantage of a low radiopacity for the majority of the hubs 307 and 305.During the procedure, the cable 310 may be coupled to the external powersource, such as RF power source 7, and can supply the radiofrequency ordirect current heating power, which emanates through the uninsulated tip303 into the surrounding bodily tissue (in this case, the intervertebraldisc material) to cause frictional heating in that nearby or proximaltissue surrounding the tip 303. In addition, the electrical cable 310may be used to sense impedance at the electrical tip 303 during theinsertion process. That is, because the inner stylet 306 is conductive,it will make electrical contact with the conductive shaft cannula 301,and thereby the tissue impedance of the tissue proximal to the exposedtip 303 may be monitored by appropriate apparatus in the externalradiofrequency generating system.

It is also possible that at or in proximity to the tip 311 of theobdurating stylet 306, there can be installed a pressure sensor 300. Inparticular, in a manner as illustrated previously with respect to FIGS.1A and 1B, the pressure sensor 300 may be exposed at least partially,such as at an outer surface of the pressure sensor 300, through anaperture 312 in the stylet shaft 306 disposed at a distance “d” upstreamfrom the exposed uninsulated tip 303 at the distal end of the styletshaft, and further exposed at least partially through a coincidentaperture 314 in the cannula 301, thereby enabling the pressure sensor300 to sense pressure within the disc 212 (see FIG. 2). Pressure sensor300 instrumentation cable or wire 350 is coupled to the pressure sensor300 and passes through the stylet 306 either separately from or embeddedwithin cable 310.

Alternatively, or in addition, as illustrated in FIG. 3A, a pressuresensor such as the pressure sensor 300 may be disposed at the exposeduninsulated tip 303 of the stylet shaft 306 and at least partiallyexposed to the disc 212 (see FIG. 2) via an aperture 316 at theuninsulated tip 303, thereby again enabling the pressure sensor 300 tosense pressure within the disc 212 (see FIG. 2). In addition, also asdiscussed previously with respect to FIGS. 1A and 1B, a temperaturesensor 320 may be disposed at the exposed uninsulated tip 303 of thestylet shaft 306 and used in conjunction with pressure sensor 300 eitherat the aperture 312 (see FIG. 3) or at the aperture 316 (see FIG. 3A).

Thus, in such a configuration, after appropriate impedance monitoring,X-ray target confirmation, etc., the radiofrequency power can be appliedthrough the cable 310, and the pressure and temperature of the tissuesurrounding the tip 303 may be monitored during the heating process bythe pressure sensor 300 and the temperature sensor 320.

Those skilled in the art will recognize that RF generator 207 may alsoserve as a temperature monitoring apparatus which may be adapted to becoupled to the stylet 306 with the stylet including the temperaturesensor 320 in proximity to the tip 303 of the stylet 306. Thetemperature sensor 320 is capable of communicating with the temperaturemonitoring apparatus represented by RF generator 207 by an electricalconnector interface represented by cable connector means 308 which canbe coupled by cable connector 309 to cable 310, which may be amultiplexer type cable transporting both power and signal to measure thetemperature of the temperature sensor 320 near the disc 212. Therefore,the temperature sensor 320 may be adapted to communicate with thetemperature monitoring apparatus represented by RF generator 207 so asto measure the temperature of the intervertebral disc 212 when the tip303 of the stylet 306 is disposed in proximity to the disc 212.

FIG. 4 shows yet another embodiment of the present disclosure. A needle414, having a cannula 401 with insulated shaft portion 402 and exposedelectrical tip 403 has a hub 405 which is made from a radiolucentmaterial such as plastic. The tip 403 is shown with a beveled point 404for purposes of illustration. It should be noted that this cannula 401,with open lumen 411, need not have a sharpened point, but rather may bea square, open lumen. In such a situation, the obdurating stylet 406 mayhave a sharpened point, which will enable effective penetration of thesystem of cannula 401 plus stylet 406 into the body. The obduratinginner stylet 406, shown as a separate part of this needle system, has inone embodiment a conductive metal shaft. Shown in this figure is abeveled tip 430, which has the same bevel angle as the beveled point 404of the respective cannula 401. A pressure sensor 400 is disposed at orin proximity to the tip 430. In particular, in a manner as illustratedpreviously with respect to FIGS. 1A and 1B, an outer surface of thepressure sensor 400 may be exposed through an aperture 412 in the styletshaft 406 disposed at a distance “d” upstream from the exposeduninsulated beveled tip 430 at the distal end of the stylet shaft 406,and further exposed through a coincident aperture 415 in the cannula401. Pressure sensor 400 instrumentation cable or wire 450 is coupled tothe pressure sensor 400 and passes through the stylet 406 eitherseparately from or embedded within cable 410. In such a situation, theradiolucent hub 407 would have a key 431, which would mate to acorresponding notch (not shown in this figure), such that when thestylet 406 is inserted into the needle 414, the beveled ends of thestylet 406 and the cannula 401 of the needle 414 will be at thecorresponding angle, such that the tip of the combination set is flushas it presents to the patient's tissue. In addition, also as discussedpreviously with respect to FIGS. 1A and 1B, a temperature sensor 420 canbe disposed at the exposed uninsulated beveled tip 430 of the styletshaft 406 and used in conjunction with pressure sensor 400. Again, thestylet 406 is illustrated with a connection cable 410 coupled to thepressure sensor 400, and the cable 410 may further be coupled toexternal apparatus such as a pressure monitoring apparatus andoptionally, impedance monitoring, stimulation, radiofrequency orhigh-power heating, and a temperature monitoring apparatus.

FIG. 5 shows yet another apparatus embodiment of the present disclosure.Again, it is a set of instruments which have appropriate design for thedisc heating application. Probe or probe electrode 500 comprises cannula501 having insulated shaft 502, with exposed tip 503 and sharpened point504. Again, a radiolucent hub 505 is coupled to the cannula 501. Needle514 is comprised of the combination of the cannula 501 and the hub 505.Also shown is a straight, multi-purpose stylet 506 with appropriatebeveled point 530. A pressure sensor 500 a is disposed at or inproximity to the beveled point 530. In particular, in a manner asillustrated previously with respect to FIGS. 1A and 1B, an outer surfaceof the pressure sensor 500 may be exposed through an aperture 512 in thestylet shaft 506 disposed at a distance “d” upstream from the exposeduninsulated beveled tip 530 at the distal end of the stylet shaft 506,and further exposed through a coincident aperture 515 in the cannula501. Pressure sensor 500 a instrumentation cable or wire 520 is coupledto the pressure sensor 500 a and passes through the stylet 506 eitherseparately from or embedded within cable 510. When this stylet 506 isinserted appropriately, the bevels 530 and 504 line up so that they areflush and present a smooth surface to the tissue that is beingpenetrated. There is an outer hub 550 which is of radiolucent materialand has the key 551 that is timed or aligned with an associated slot inthe needle hub 505 (said slot is not shown in FIG. 5) so that the bevels504 and 530 will line up appropriately. Further, it has a secondaryadjustable hub 552 which is made of radiolucent material and isimprinted with visible measuring markers 553. The user, by observingthese measuring markers 553 relative to, for example, the proximal face554 of the outer hub 550, may be able to determine, while the electrodeis in place in the body, the degree of extension of the beveled point530 of the stylet 506 relative to the sharpened point 504 of needle 514.In addition, also as discussed previously with respect to FIGS. 1A and1B, a temperature sensor 535 a can be disposed at the exposeduninsulated beveled tip 530 of the stylet shaft 506 and used inconjunction with pressure sensor 500 a. This measurement capabilitywould be appropriate for the geometry shown previously in FIG. 2 wherethe extension 251 may be extended beyond the tip 202 of shaft 280 of theneedle so as to make pressure measurements and optionally, extendedlesions or extended impedance measurements within the disc 212 itself.Thus, the straight stylet structure shown in FIG. 5 is analogous to thestraight stylet structure shown in FIG. 4, with the exception that ithas the depth gauge adaptation. In addition, a cable means 510 is alsoillustrated for connection to the external apparatus.

Further in FIG. 5 is shown a stylet 565 with shaft portion 560 and acurvilinear distal or end portion 561. The curvilinear configuration ofthe distal end 561 may be either permanently set into the stylet 565 ormay be steerable by adaption means on the primary hub 564. Primary hub564 is analogous or identical to the hub 550 of the straight stylet 506.Again, depth gauge means 562, with depth markers 563, are provided forthe operator to gauge the degree of extension of the curved tip 561. Apressure sensor 500 b is disposed at or in proximity to the distal endportion or tip 561. In particular, in a manner as illustrated previouslywith respect to FIGS. 1A and 1B, an outer surface of the pressure sensor500 b may be exposed through an aperture 574 in the stylet shaft 560disposed at a distance “d” upstream from the exposed uninsulated curvedtip 561 at the distal end of the stylet shaft 560. Pressure sensor 500 binstrumentation cable or wire 570 is coupled to the pressure sensor 500b and passes through the stylet 565 either separately from or embeddedwithin cable 572. In addition, also as discussed previously with respectto FIGS. 1A and 1B, a temperature sensor 535 b can be disposed at theexposed curved tip 560 of the stylet shaft 560 and used in conjunctionwith pressure sensor 500 b. The gauging of the degree of extension ofthe curved tip 561 would be exemplified by the illustration of FIG. 2for extended off-axis measurements or heating. Such off-axis heatingwould be appropriate when difficult approaches to the disc 212 arerequired. An example of this would be the L5-S1 disc, which, in somecases, requires the needle to be placed in a direction that is notpassing through the center of the disc. In such a situation, the needletip 504 may be off-center from the disc, yet the side extension curve,such as 561 of the stylet 565, may be directed off-axis to bring theaverage center of lesioning back to approximately the center 250 of thedisc 212. This combination of instruments in FIG. 5 represents yetanother apparatus embodiment which would be suitable for the discheating procedure.

Still another way of measuring the pressure throughout the disc and atremote positions would be to have a keyed slot in the hub of the probesuch that the probe is then moved a fixed distance each time that thekey is positioned within the slot. More particularly, FIGS. 5A and 5Billustrate needle 514 of FIG. 5 being comprised of a hub 581 having akey slot 582 extending along a portion of the length of the hub 581,with the key slot 582 further including at least two openings, e.g., adistal notch 584 and a proximal notch 585, separated from each other bya distance D along the length of the hub 581 and being formedtransversely with respect to the key slot 582 and in communicationtherewith for engaging a key portion 583 which is connected to thestylet 506 and to a stylet extender handle 585. In FIG. 5A, with thestylet 506 being in the retracted position with respect to the needle514, the beveled point 530 of stylet 506 is flush with the sharpenedpoint 504 of the needle 514. In this position, the key portion 583 isengaged in the proximal notch 584. In FIG. 5B, via rotation of theextender handle 586, the key portion 583 is disengaged from the proximalnotch 584 and via translation along the length of the key slot 582towards the distal notch 585, the beveled point 530 of the stylet 506 ismoved to an extended position equal to dimension D with respect to thesharpened point 504 of needle 514. Upon rotation of the extender handle586, the key portion 583 is then engaged with the distal key opening585. To return to the retracted position illustrated in FIG. 5A, theprocedure is reversed. Those skilled in the art recognize that thestylet 565 with the shaft portion 560 and curvilinear distal or endportion 561 can be similarly extended and retracted via the extenderhandle 586 and the hub 581 with the key slot 582, key portion 583, andnotches 584 and 585. The foregoing embodiment of the extender handle 586and the hub 581 with the key slot 582, key portion 583, and notches 584and 585 ensures accuracy of the pressure monitoring readings andrepeatability of locating the pressure sensor at previously monitoredpositions.

An exemplary embodiment is seen in FIG. 6. For example, FIG. 6 shows anelectrode embodiment which requires only one structure to do multiplefunctions. Probe or probe electrode 600 comprises a shaft 601 which isinsulated over its surface 602 and has an exposed tip 603. The tip 603,in this case, is illustrated with a point 604 that has a trocar shape,as opposed to a planar, angular bevel. This merely illustrates thatthere are a variety of ways of implementing a tissue-piercing point.Disposed at or in proximity to the tip 603 is a pressure sensor 600 afor reading the tissue pressure during heating. In particular, in amanner as illustrated previously with respect to FIGS. 1A and 1B, anouter surface of the pressure sensor 600 a may be exposed through anaperture 612 in the shaft 601 disposed at a distance “d” upstream fromthe exposed trocar tip 604 at the distal end of the shaft 601. Pressuresensor 600 a instrumentation cable or wire 620 is coupled to thepressure sensor 600 a and passes through the shaft 601 either separatelyfrom or embedded within cable 610, which may be a multiplexer typecable. In addition, also as discussed previously with respect to FIGS.1A and 1B, a temperature sensor 630 can be disposed at the exposeduninsulated trocar tip 604 of the shaft 601 and used in conjunction withpressure sensor 600 a. The hub 605 is substantially radiolucent so as toenable the possibility of the needle view or tunnel vision radiographicmonitoring. The cable 610 connects to the shaft 601, and thus to theexposed tip 603 as a supply of radiofrequency power. This structure canbe inserted into the tissue and serve the multiple functions of pressuremonitoring, impedance monitoring, RF power delivery, temperaturemonitoring, etc. Thus, it obviates the need for multiple cannulae andstylets. It has the obvious deficit that, if one wishes to injectcontrast media or local anesthetic, it would not be possible without anopen lumen needle cannula, as illustrated in FIGS. 2 to 4, or injectionand exit holes on the hub and tip of the electrode. However, sinceinjection of such fluids in some situations is not a requirement, theelectrode system illustrated in FIG. 6 would be an adequate embodimentof the present disclosure.

In a variation of the present disclosure, FIGS. 7A and 7B illustrate anelectrode 702 having a tip 704 at a distal end and an aperture 710formed within tip surface 706. The tip surface 706 is formed at an angleresulting in a sharpened point, thereby enabling penetration of bonematerial by the tip 704. A pressure sensor 700 may be disposed at thedistal end in a recessed position internally to the electrode 702 suchthat the surface of the pressure sensor 700 exposed by the aperture 710does not protrude beyond the surface 706 of the tip 704. In thisvariation of the present disclosure, thermocouple 50 may be disposed onsurface 706 adjacent to pressure sensor 700 such that measurements ofboth parameters, i.e., pressure and temperature, are with respect totissue at the surface 706.

A pressure sensing cable 720 is coupled to the pressure sensor ortransducer 700 and, in a manner similar to that previously discussedwith respect to FIG. 1, is routed through the multiplexing cable 6 tocouple with the pressure monitor 10. A temperature sensing cable 760 iscoupled to the thermocouple 50 and also routed through the multiplexingcable 6 to couple with the pressure monitor 10. Those skilled in the artrecognize that the foregoing configuration of pressure sensor 700 andthermocouple 50 can substitute for the previously disclosedconfigurations of pressure sensors and temperature sensors of FIGS. 1,2, 3, 4, 5, 5A, 5B, and 6 wherein the pressure sensor is disposed at adistance “d” upstream of the tip of the electrode or stylet at thedistal end.

This disclosure is not limited to back pain, but may be applied at anyof the intervertebral disc levels from the top to the bottom of thespine. For example, it can be used in treating thoracic or neck pain atthe appropriate spinal levels. The disclosure is also not restricted topercutaneous needle placement. For example, in the process of doing anopen surgical laminectomy, which is a very common procedure, a surgeonmay wish to insert such a probe or electrode as has been describedherein directly into the exposed disc so that the tip of the probe thenresides in the interior of the disc. By this means, radiofrequency orother power sources may be coupled to the electrode so as to heat theintervertebral disc directly under open exposure. Monitoring of the discpressure and temperature under such conditions can be done directly atthe periphery of the disc. The interruption of the neural structures asdescribed above would also pertain for this “open procedure.”

Energy therapies as disclosed herein are used also to shrink tissue inmany orthodpedic applications such as in treating laxities of theshoulder and other joints. Pressure monitoring as disclosed herein maybe usefully applied in such orthopedic applications as well.

There are many variations on the present disclosure which might bepossible. Combinations of impedance monitoring, stimulating, andtemperature monitoring in conjunction with the pressure monitoring andheating method have been described and can be used. How the pressuresensor and the temperature sensor are synchronized with the applicationof RF energy is dependent on the types of sensors used. Typicalthermocouples and pressure transducers use small electrical current forsensing which is easily disrupted by large RF outputs, so the samplingof these sensors is done during RF off times when the duty cycle ofthese outputs allow. More complicated methods of sampling these sensorsduring RF on times is possible with filtering, etc. but is expensive torealize.

When the temperatures within the spinal disc rise above the boilingpoint, the spinal fluids change phase to gas and then the universalperfect gas law generally applies, i.e., PV=nRT, (where P is absolutepressure, e.g., in Newtons/meter² or Pascals, V is volume, e.g., inmeter³, n is the number of moles, mol, of gas, R is the universal gasconstant in appropriate units, e.g., Joules/mol-degree Kelvin, and T istemperature, e.g. in degrees Kelvin or ° K), which can make measurementsfrom the pressure sensor less reliable because areas of phase change donot represent properly the overall tissue pressure. Since optical signaltransmission is unaffected by proximate electric or magnetic fieldsgenerated by radiofrequency current, the use of optical signaltransmission may allow easier adaptation of electrodes for use withmagnetic resonance imaging.

It is also not necessary that the source of heating of the disc beradiofrequency current. It could alternatively be microwave current ordirect current heating. In the case of direct current heating, one coulduse for example a nichrome wire inside the probe to create ohmic heat ofthe tip at a location within the disc. The heat would spread by thermalconduction throughout the disc and give rise to a similar effect on theneural structures as described above. RF heating has advantages in thatit deposits the heat energy at longer range relative to the tip, andthus has the feature of distributing the heat throughout the disc in aneffective way. The heating may be by penetrating radiation such asultrasound or microwaves that are absorbed by the disc with or without aprobe being placed in the disc. A ferromagnetic seed might be placed inthe disc, and it is heated in turn by induction from external waves orbeams. Thus, the “probe” may mean any object placed in the disc that isan agent to cause heating of the disc.

The disc heating may be done in conjunction with other intervertebralsurgery or instrumentation. For example, the tools that are used duringpercutaneous discectomy such as a cutting tool may serve also as aheating probe. The disc heating can be done simultaneously or as anadjunct to other disc treatment. This may as well apply to open surgicallaminectomy (disc surgery) at which time tools or probes may serve asagents to heat the disc according to the present disclosure.

Stereotactic apparatus and other guidance techniques could be used toplace the tip of the electrode at a desired target within the disc or atseveral targets within the disc in sequence. Clusters of heating probescould be used to more effectively deposit heat throughout a volume of adisc. Such variations are obvious to those skilled in the art and aremeant to be included in the scope of the present disclosure.

While the disclosure has been illustrated and described, it is notintended to be limited to the details shown, since various modificationsand substitutions can be made without departing in any way from thespirit of the present disclosure. As such, further modifications andequivalents herein disclosed can occur to persons skilled in the artusing no more than routine experimentation, and all such modificationsand equivalents are believed to be within the spirit and scope of thedisclosure as defined by the following claims.

1. A probe system for treating an intervertebral disc of a patient,comprising: a probe, the probe comprising: a cannula having a proximalend and a distal end and having an open end defined at the distal endthereof, said cannula adapted to couple to a power source; a stylethaving a proximal end and a distal end, said stylet fitting into saidcannula so that the distal end of the stylet occludes said open end atsaid distal end of said cannula; and a pressure monitoring apparatusadapted to be coupled to said stylet, said stylet including a pressuresensor in proximity to the distal end of said stylet, said pressuresensor adapted to communicate with said pressure monitoring apparatus soas to measure the pressure of the intervertebral disc, wherein the powersource delivers power to said distal end of said cannula, causingheating of the disc when said distal end of said cannula is disposedwithin the disc, to relieve patient pain associated with the discthereby.
 2. The probe system in accordance with claim 1, wherein saidpressure sensor is disposed in an aperture defined in proximity to thedistal end of said stylet, and said pressure sensor is at leastpartially exposed through said aperture in said stylet, to sensepressure in the disc thereby.
 3. The probe system in accordance withclaim 1, wherein said stylet has a tip at the distal end of said stylet,said tip of said stylet having an aperture defined therein, and saidpressure sensor is at least partially exposed through said aperture atsaid tip, to sense pressure in the disc thereby.
 4. The probe system inaccordance with claim 1, wherein said cannula is substantially insulatedon a surface of said cannula in communication with the body of thepatient including the intervertebral disc, said cannula having anuninsulated electrically conductive tip at the distal end of saidcannula, said uninsulated electrically conductive tip adapted to coupleto said power source such that when said distal end of said cannula iswithin the disc, power can be transmitted to heat the disc.
 5. The probesystem in accordance with claim 4 further comprising: an impedancemonitoring apparatus adapted to be coupled to said stylet by electricalinterface to monitor the tissue impedance of the patient to confirm theproper placement of said distal end of said cannula inside of the disc.6. The probe system in accordance with claim 1 further comprising: atemperature monitoring apparatus adapted to be coupled to said stylet,said stylet including a temperature sensor in proximity to the tip ofsaid stylet, said temperature sensor adapted to communicate with saidtemperature monitoring apparatus so as to measure the temperature of theintervertebral disc when the tip of said stylet is disposed in proximityto the disc.
 7. A method of treating back or neck pain of a patient byheating an intervertebral disc, comprising the steps of: providing aprobe having a proximal end and a distal end, said distal end having atip, said probe operatively coupled to a power source; providing apressure sensor in proximity to said tip of said probe and a pressuremonitoring apparatus operatively coupled to the pressure sensor via theprobe; delivering power from said power source to said distal end ofsaid probe, causing heating of the disc when the distal end of the probeis disposed within the disc, to relieve patient pain associated with thedisc thereby; and measuring pressure of the disc.
 8. The methodaccording to claim 7, wherein the step of delivering power from saidpower source to said disc via said probe is performed for a period ofapproximately one minute.
 9. The method according to claim 8, whereinimmediately following the step of delivering power from said powersource to said disc via said probe, the method further comprises thestep of turning off the power.
 10. The method according to claim 9,wherein following the step of turning off the power, the method furthercomprises the steps of waiting for a period of approximately one minuteand measuring the pressure sensed by the pressure sensor.
 11. The methodaccording to claim 10, wherein, if it is determined that furthertreatment is necessary based upon the measured pressure in that asubstantial change in disc pressure to a pressure level below athreshold pressure has not been achieved, the method further comprisesthe step of re-delivering power from said power source to the disc viasaid probe causing heating of the disc.
 12. The method in accordancewith claim 7, wherein said probe is a radiofrequency electrode and saidpower source is a radiofrequency generator, the method furthercomprising the steps of: increasing voltage output of saidradiofrequency generator so as to send current through saidradiofrequency electrode into the disc and thus heat the disc by ohmicheating; and decreasing the voltage output of said radiofrequencygenerator after a change in disc pressure has been measured.
 13. Themethod in accordance with claim 7, wherein said pressure sensor isdisposed in proximity to said tip of said distal end of said probe, saidprobe having an aperture disposed such that said pressure sensor is atleast partially exposed through said aperture in said probe, thereby tosense pressure in the disc.
 14. The method in accordance with claim 7,wherein said pressure sensor is disposed at said tip of said distal endof said probe, said probe having an aperture disposed such that saidpressure sensor is at least partially exposed through said aperture,thereby to sense pressure in the disc.
 15. A method of treating back orneck pain of a patient by heating the interior of an intervertebraldisc, comprising the steps of: providing a probe, the probe having aproximal end and a distal end having a tip, said probe coupled to apower source; providing a pressure sensor at one of at and in proximityto said tip of said probe and a pressure monitoring apparatusoperatively coupled to said pressure sensor via said probe; insertingsaid probe into said patient so that said tip at said distal end of saidprobe is positioned inside the intervertebral disc; delivering power viasaid probe to said probe tip so as to heat tissue around said probe tipwhen said probe tip is in the intervertebral disc so that said probe tipcauses heating of the interior of the intervertebral disc to atemperature substantially above body temperature by absorption of atleast a portion of said power delivered via said probe tip to the tissueof the intervertebral disc, thereby causing heating and resultantchanges in the disc material and nearby neurological structures torelieve the patient's pain; and monitoring pressure of theintervertebral disc by reading output of said pressure monitoringapparatus operatively coupled to said pressure sensor, and therebyquantitatively monitoring said heating process of the intervertebraldisc.
 16. The method in accordance with claim 15, wherein said pressuresensor is disposed in proximity to said tip of said distal end of saidprobe, said probe having an aperture disposed such that said pressuresensor is at least partially exposed through said aperture in saidprobe, thereby to sense pressure in the disc.
 17. The method inaccordance with claim 15, wherein said pressure sensor is disposed atsaid tip of said distal end of said probe, said probe having an aperturedisposed such that said pressure sensor is at least partially exposedthrough said aperture in said probe, thereby to sense pressure in thedisc.
 18. The method according to claim 17, wherein the step ofdelivering power is performed for a period of approximately one minute.19. The method according to claim 18, wherein immediately following thestep of delivering power, the method further comprises the step ofturning off the power.
 20. The method according to claim 19, whereinfollowing the step of turning off the power, the method furthercomprises the steps of waiting for a period of approximately one minuteand reading the output of the pressure monitoring apparatus operativelycoupled to said pressure sensor.
 21. The method according to claim 20,wherein, if it is determined that further treatment is necessary basedupon the measured pressure in that a substantial change in disc pressureto a pressure level below a threshold pressure has not been achieved,the method further comprises the step of: re-delivering power from saidpower source to the disc via said probe causing heating of the disc.